Many laser processing systems use a process spot with a specified spatial intensity profile at a work surface to optimize a particular laser process. Beamshaping methods for producing the desired spatial intensity profile include, for example, using diffractive and refractive optic elements. These approaches pose design challenges, however, due to restrictive input laser beam tolerances (e.g., for position, diameter, mode quality, and other parameters) generally required to maintain acceptable output beam characteristics. Production laser processing systems are generally designed to meet such output laser beam characteristics despite variations in input laser beam characteristics and/or laser beam delivery optics. Such variations may occur, for example, over time, as temperature changes, and/or with variations in system components (e.g., from one system to another system).
Typical approaches for generating a laser beam with a desired spatial intensity profile use pre-designed hard optical elements, which rely on certain beam characteristics for proper operation. For example, a diffractive optical element (DOE) produces a shaped beam with desired characteristics (e.g., peak intensity variation, spatial cutoff band, maximum sidelobe amplitude, and other characteristics) when used with a Gaussian beam that has a particular centroid, X and Y diameter, spatial mode content, and wavefront error. The output shaped beam characteristics degrade, however, as the input beam characteristics deviate from the specifications used to design the DOE.
Because a DOE is generally made for a particular application, the output beam shape cannot be easily modified once the DOE is designed. Thus, if a particular laser process uses a new output beam shape or a variety of output beam shapes for optimum process quality or speed, the existing methods that use pre-designed hard optical elements are cumbersome and/or impractical. An exception to this is the manipulation of the output beam by scaling (e.g., through variable magnification) and rotation (e.g., through devices such as Dove prisms). These methods are adequate in some applications but may be inadequate or restrictive other applications.